Topic Contents

Sedimentation Rate (Sed Rate)

Test Overview

The sedimentation rate (sed
rate) blood test measures how quickly red blood cells (erythrocytes) settle in
a test tube in one hour. The more red cells that fall to the bottom of the test
tube in one hour, the higher the sed rate.

When
inflammation is present in the body, certain
proteins cause red blood cells to stick together and
fall more quickly than normal to the bottom of the tube. These proteins are
produced by the liver and the
immune system under many abnormal conditions, such as
an infection, an
autoimmune disease, or cancer.

There are
many possible causes of a high sedimentation rate. For this reason, a sed rate
is done with other tests to confirm a diagnosis. After a diagnosis has been
made, a sed rate can be done to help check on the disease or see how well
treatment is working.

Why It Is Done

A sedimentation rate (sed rate) test is
done to:

Find out if inflammation or infection is
present.

Check on the progress of a disease.

See how
well a treatment is working.

How To Prepare

You do not need to do anything before
you have this test.

Talk to your doctor about any concerns you
have regarding the need for the test, its risks, how it will be done, or what
the results will mean. To help you understand the importance of this test, fill
out the
medical test information form(What is a PDF document?).

How It Is Done

The health professional drawing blood
will:

Wrap an elastic band around your upper arm to
stop the flow of blood. This makes the veins below the band larger so it is
easier to put a needle into the vein.

Clean the needle site with
alcohol.

Put the needle into the vein. More than one needle stick
may be needed.

Attach a tube to the needle to fill it with
blood.

Remove the band from your arm when enough blood is
collected.

Apply a gauze pad or cotton ball over the needle site as
the needle is removed.

Apply pressure to the site and then a
bandage.

How It Feels

The blood sample is taken from a vein in
your arm. An elastic band is wrapped around your upper arm. It may feel tight.
You may feel nothing at all from the needle, or you may feel a quick sting or
pinch.

Risks

Blood test

There is very little chance of a
problem from having a blood sample taken from a vein.

You may get a small bruise at the puncture
site. You can reduce the risk of bruising by keeping pressure on the site for
several minutes after the needle is withdrawn.

In rare cases, the
vein may become inflamed after the blood sample is taken. This condition is
called phlebitis and is usually treated with a warm compress applied several
times daily.

Continued bleeding can be a problem for people with
bleeding disorders. Aspirin, warfarin (Coumadin), and other blood-thinning
medicines can also make bleeding more likely. If you have bleeding or clotting
problems, or if you take blood-thinning medicine, tell your health professional
before your blood is drawn.

Results

Normal

The normal values listed here-called a reference range-are just a guide. These ranges vary from lab to lab, and your lab may have a different range for what's normal. Your lab report should contain the range your lab uses. Also, your doctor will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed here may still be normal for you or your lab.

What Affects the Test

Medicines. Many medicines can change the results of this test.
Be sure to tell your doctor about all the nonprescription and prescription
medicines you take.

What To Think About

Even though some problems, such as giant cell
arteritis, almost always cause a high sedimentation rate (sed rate), the test
can't be used by itself to identify a specific disease. Results of a sed rate
test are considered along with your symptoms, other test results, and medical
information.

Some diseases that cause inflammation do not increase
the sed rate, so a normal sed rate does not always rule out a disease.

Some doctors use the C-reactive protein (CRP) blood test instead
of the sed rate test to help identify inflammatory conditions. To learn more, see the topic
C-Reactive Protein (CRP).

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